A brushless structure is one of the major features of a DC brushless motor which in principle generates no noises. The noises include not only mechanical noises, but also electrical noises. Moreover, as the brushless motor negates the contacting between certain components therein, it is easier to make a high-speed rotary motor by using such a motor.
When the DC brushless motor is driven, a Hall signal output from a Hall element is often used as the starting point of a sine wave. Ideally, when the Hall element is arranged with no mounting tolerance, no phase difference exists between a back EMF, a driving voltage and the Hall signal, and between the driving current and the Hall signal.
However, in an actual manufacturing process, the positional tolerance of the Hall element affects the quality of a motor manufactured in mass production. For example, while the Hall signal is in-phase with the driving voltage, due to the mounting tolerance of the Hall element, the phase of the back EMF will lead that of the driving voltage, which will cause an increase in the feedback current and undesired power consumption by the brushless DC motor, and thus reduce the efficiency of the DC brushless motor.
Therefore, it is very important to improve the current circuit design with a motor driving circuit capable of automatic adjustment to eliminate the offset of the Hall element.